1. Field of the Invention
The present invention relates to polyimides. In particular, it relates to polyimides containing the cyclobutene-3,4-dione chemical moiety.
2. Description of the Related Art
Because of their outstanding thermal stability, low density, electrical insulating capability, and toughness and stability to organic solvents, linear aromatic polyimides are used for applications in the electronics and aerospace industries. They are especially attractive to these industries because of their toughness, flexibility, and ability to be formed into complex shapes both with and without reinforcements such as glass or graphite fibers. In the electronics industry, polyimides are widely used as dielectric interlayers because of their high dielectric constants and their ability to form uniform coatings over a variety of substrates.
The need exists for high temperature polymers such as polyimides which can be processed into films, adhesives, and coatings that can withstand a highly oxidative environment. This environment is often seen on the outer structural surfaces of supersonic aircraft; jet engine components; and on spacebased devices. However, the application of most polyimides are limited by their glass transition temperatures (Tgs) which, when approached, causes a decrease in their mechanical properties which can result in debonding, creep, and delamination.